Typically with controlled path computer operated robot arms the path of the controlled point associated with the end of the robot arm, i.e. the tool centerpoint, is determined during the teaching or programming mode of operation. In the teaching mode, a number of predetermined points are defined and stored; and during the automatic mode of operation, the robot control generates a predetermined path between the programmed points. Once this programmed path is defined, it is fixed and unchangeable during the automatic mode of operation. However, there are many situations in which the actual process requires that the relationship between the robot arm and the workpiece be different from the relationship that was taught.
For example, in a seam welding application, the actual seam location will be different from one workpiece to the next; and the programmed path will be inadequate to control the tool centerpoint along the seam when using the same program to weld a number of workpieces. Consequently, there is a requirement that the programmed path be modifiable during the automatic mode of operation, i.e., the relationship between the tool centerpoint and the workpiece be dynamically adjusted between the predetermined points. Although there may be many techniques for solving this problem, two variations will be disclosed.
First, the operator may be provided with a control stick having forward, backward, left and right motions which represent respective up, down, left and right deviations from the program path. During the automatic mode of operation, the operator observes the relationship between the tool centerpoint and the seam and moves the control stick to command the necessary deviations from the programmed path to maintain the tool centerpoint in the correct relationship to the seam. The control stick motion energizes contacts which are connected to the robot control. The robot control detects the contact inputs and executes an appropriate path modification.
In another embodiment, a seam following apparatus may be attached to the end of the robot arm which moves along the programmed path. As this apparatus detects deviations of the seam from the programmed path, it energizes contacts which define the direction of the deviation to the robot control. The control then modifies the path to correspond to the detected deviations. There are other applications in which it may be desirable to change the relative position of the tool centerpoint to the workpiece from the programmed relationship. For example, the robot may be required to follow the contour of an edge of a workpiece for deburring or a flashing removal operation. In these situations, the contour of the edge may vary from one workpiece to another.
It is therefore one object of the present invention to provide a means by which an operator may effect changes of motion of a tool centerpoint associated with a function element of a robot arm during an automatic mode of operation.
It is a further object of the present invention to effect changes of motion from a predetermined path between two programmed points during an automatic mode of operation.
It is a further object of the present invention to effect changes of motion from a predetermined path in response to deviation signals produced automatically by workpiece processing related apparatus during an automatic mode of operation.
It is a further object of the present invention to generate offset paths displaced from predetermined paths in response to deviation signals whether manually or automatically produced.